Investigation on the possible control of grain size on development of ‘mud cracks’: a preliminary experimental study of recent Gangetic alluvial samples, West Bengal, India

The so-called mud cracks, possibly the most common deformation feature in sediment, are evident in almost all dried-up exposed sediment surfaces. Several experimental attempts have so far been made to explain the evolution of mud cracks. However, most of the experiments were carried out with bentonite clay or other artificial substances in controlled heating condition. Therefore, those experiments could not or were not performed to elucidate the control of grain size on crack development although it has been observed that cracks develop in almost all types of soil. The present work is an attempt to understand the control of sediment grain size in development and evolution of these cracks. This experimental study was carried out in near-natural condition. Sediment samples of three different grain-size fractions ranging from sub-sand size to very coarse sand size were used for the experiment. The 10-day-long experiment with watering and drying of the samples under sunlight shows that the time gap between watering and appearance of cracks, smoothness of crack walls, number of cracks and also number of polygons with cracks as their arms are dependent on grain size of the sediment.